The present invention is based on the inclusion of a water-soluble modified resin.
This invention pertains to coatings, sometimes referred to as varnishes, and particularly pigmented coatings, or inks, in which the primary binder is a soluble modified rosin resin, and the primary solvent is water.
Modified rosin resins, including particularly fumaric acid- and maleic anhydride-modified rosin resins, are well known, as are phenol-modified rosin resins, all of which are sometimes used as carrier resins in package coatings, usually referred to as varnishes, and inks, including magazine and newsprint inks. However, practical embodiments of such coating compositions have generally all been non-aqueous solvent based. Economics and environmental concerns provide an incentive for the development of aqueous-based resin coatings. Whereas some fumaric acid-modified and maleic anhydride-modified rosin resins work in aqueous coatings, practical phenol-modified rosin compositions for this purpose have been effectively unavailable, due primarily to the absence of a suitable water-soluble modified rosin resin.
Compositions in this general field and including some of these characteristics are disclosed in the prior art U.S. patents identified below, all of which have been considered in conjunction with the preparation of the present patent application, namely:
______________________________________ 2,776,895 Biser, 3,468,829 Yoshioka et al, 3,674,732 Pitzalis et al. 3,880,788 Rudolphy, 4,075,143 Schelhaas et al, and 4,391,640 Okoshi et al. ______________________________________
All of the above references pertain to solvent-based varnishes and inks. In each of these references, a resin is included which is a modified rosin, in some cases a phenol or phenolformaldehyde-modified rosin.